Device by pipeline diversion

ABSTRACT

A device at a pipeline connection for connection of a pig launching/receiving device ( 34 ) and/or a connecting pipe ( 36 ) to a submerged pipeline ( 3 ), and where the pipeline ( 3 ) is communicatingly connected to a first deflection bend ( 4 ) from which a blind pipe ( 8 ) projects from the first deflection bend ( 4 ) substantially concentrically with and in the opposite direction of the pipeline ( 1 ), preferably not in communication with the deflection bend ( 4 ).

[0001] This invention regards a device for simplifying remoteconnection/disconnection of equipment to a pipeline on the seabed. Inparticular, the invention regards a pipe deflection where connection anddisconnection to a subsea pipeline of another pipe and/or a device forlaunching and receiving a pig may be carried out by means of said remoteconnection and possibly an ROV, especially for use in connection withsubsea pipelines of the type commonly used in connection with theproduction and transportation of petroleum. The preferred designationfor the invention is “trunnion bend pieces”.

[0002] When laying pipelines on the seabed, it is common according toprior art for the lay vessel to lower the free end portion of the pipedown to the seabed.

[0003] During pipe maintenance, pigs are sent through the pipe e.g. toclean, check and/or test the pipe. According to prior art, a separatemanifold/structure is installed on the seabed by means of a liftingvessel brought to the site, whereupon the pipeline is pulled into andconnected to the manifold.

[0004] Alternatively, the end portion of the pipeline may be lifted tothe surface, where a manifold is welded on. Then the pipeline can bere-installed.

[0005] According to prior art, a shroud is normally constructedunderneath valves and couplings that are to be installed directly inline with the pipeline. The shroud ensures an even transition betweenthe pipe and the bottom profiles of the valves/couplings, which isrequired in order to enable the valves/couplings to be passed acrossrollers on the lay ramp of the lay vessel. Furthermore, the shroud iscommonly used to ensure that the end portion of the pipe does not sinkinto the seabed, whereby the end opening of the pipe would beinaccessible. The underlying shroud will distribute the weight of thepipe and the manifold over a somewhat larger area.

[0006] Separate structures of this type require extensive constructionand fabrication work. A lack of standardisation makes it necessary to dothe construction work again for each pipe, and to tailor e.g. themaintenance work to each particular case. The underlying shroud at theend portion of the pipe must extend along a relatively long section ofthe end portion of the pipe in order to be able to pass across the layramp of the lay vessel. Valves welded directly to the pipeline aresubjected to relatively large bending moments, thus being prone todamage or becoming less reliable in operation.

[0007] It appears that the risk of hydrocarbon leaks/spills increaseswith the number of connections. Thus the relatively large number ofconnections associated with prior art manifolds is a disadvantage.Installing a pipe with a separate manifold involves the lay vesselhaving to spend extra time in order to arrange and connect the manifoldto the pipe, or optionally the use of a lifting vessel to carry out theconnecting operation. Consequently, the connecting operation isunnecessarily expensive.

[0008] The object of the invention is to remedy the disadvantages ofprior art.

[0009] The object is achieved in accordance with the invention by thecharacteristics given in the description below and in the appendedclaims.

[0010] Arranging a connection device for a pig launching/receivingdevice at a level slightly above the seabed avoids the connection devicesinking into the seabed. According to the invention, the pipeline isequipped with a first bend at a distance from the end portion of thepipeline, whereby the hydrocarbon carrying pipe is deflected. Thepipeline, preferably without fluid connection with the hydrocarboncarrying pipe, is substantially concentric with and extends in theopposite direction of the pipeline from the first bend and on to the endportion of the pipeline, where it is connected to a pad eye.

[0011] The hydrocarbon carrying pipe is deflected preferably to ahorizontal position by means of a second bend, and is equipped with ashut-off valve and a connection device for a pig launching/receivingdevice.

[0012] By giving the deflection the appropriate design, it becomespossible to lead the deflection with valves and couplings down to theseabed as part of the pipeline, via the lay ramp of the lay vessel.

[0013] The deflected pipe is well suited e.g. for branching off a pipefor remote connection to a subsea installation.

[0014] Advantageously, said valves and connection devices may becontrolled remotely according to techniques that are known per se.

[0015] The following describes a non-limiting example of a preferredembodiment illustrated in the accompanying drawings, in which:

[0016]FIG. 1 is a perspective view of a deflection according to theinvention, where a pig launching/receiving device is connected to thedeflection, and where a connecting pipe is being connected;

[0017]FIG. 2 is a schematic diagram of a deflection on its way down tothe seabed from a pipelaying vessel;

[0018]FIG. 3 is a partially sectioned side view of the deflection ofFIG. 1 as a pig launching/receiving device is on its way down from thesurface;

[0019]FIG. 4 shows a cutout of FIG. 2 on a larger scale. The pipelinedeflection is shown emphasized and comprises a first bend, a blind pipe,a transition piece and a second bend;

[0020]FIG. 5 shows the same as FIG. 3, but here, the piglaunching/receiving device is connected to the deflection;

[0021]FIG. 6 shows the same as FIG. 5, but here, a connecting pipe is onits way down from the surface;

[0022]FIG. 7 shows the same as FIG. 6, but here, the connecting pipe hasbeen lowered and is ready for connection to the deflection; and

[0023]FIG. 8 shows the same as FIG. 7, but here, the connecting pipe hasbeen connected to the deflection.

[0024] In the drawings, reference number 1 denotes a deflection pipearranged on the seabed 2, comprising a pipeline 3, a first bend 4connected to the pipeline 3 and also to a transition piece 6, here shownas a T-piece, and a blind pipe 8 extending from the first bend 4 andessentially coaxially with the pipeline 3, from the bend 4 to a pad eye10. The blind pipe 8 and the pad eye 10 constitute the end portion ofthe pipeline.

[0025] The transition piece 6 is further connected to a second bend 12that is connected to a remote connection 16 via a valve 14 and to aremote connection 22 via a third bend 18 and a valve 20. The valves 14,20 and the remote connections 16, 22 are of types that are known per seand designed to be operated remotely by e.g. an ROV.

[0026] The pipeline 3 and the blind pipe 8 are equipped with thenecessary fixing brackets 24 for fixing the remote connections 16, 22, afirst vertical column 26 and a second vertical column 28. The columns26, 28 are connected to guide cables 30 and 32 respectively, extendingto the surface. The column 26 and the guide cable 30 are designed toguide a pig launching/receiving device 34 during lowering from thesurface down to the deflection 1, where it fits the remote connection 16in a complementary manner.

[0027] The column 28 and the guide cable 32 are designed to guide aconnecting pipe 36 during lowering from the surface down to thedeflection 1, where it fits the remote connection 22 in a complementarymanner.

[0028]FIGS. 3 and 5 show a pig launching/receiving device 34 that islowered in accordance with known techniques via the guide cable 30 andthe column 26 and then connected to a remote connection 16, while FIGS.6, 7 and 8 show a connecting pipe 36 that is lowered in accordance withknown techniques via the guide cable 32 and the column 28, whereupon itis connected to the remote connection 22.

[0029] When a deflection 1 is to be laid on the seabed 2 to form an endportion of the pipeline 3, it is connected to the pipeline 3 on board apipelaying vessel 38 e.g. by welding, before it is passed across the layramp 40 of the pipelaying vessel and down into the sea 42, see FIG. 2.Once it is laid on the seabed 2, the deflection 1 may be disconnectedfrom the laying cable 44 of the pipelaying vessel 38, and is then readyfor connection to the connecting pipe 36 without requiring extensivesupplementary work. Pig launching/receiving devices 34 are normallyconnected during the laying of the pipe, and may readily be retrieved tothe surface and reinstalled with new pigs.

[0030] When compared with prior art, the invention helps tosignificantly simplify and reduced the costs of laying, connecting,starting up and maintaining subsea pipelines 3. The deflection 1 furtherexhibits several favourable characteristics in that the blind pipe 8continues as a part of and preferably with the same dimension as thepipeline 3, the valves are not subjected to bending moments duringlaying or operation, the pipeline 3 and the blind pipe 8 rest on theseabed in a known manner without requiring an underlying additionalshroud or other framework to support the deflection 1. The mechanicalconnections may be executed in the same manner as for known connectingtees.

[0031] The deflection 1 is suitable for use with standardised toolsdesigned to carry out all forms of pigging operations.

1. A device by a pipeline connection for connection of a piglaunching/receiving device and/or a connecting pipe to a submergedpipeline, wherein the pipeline is communicatingly connected to a firstdeflection bend from which a blind pipe projects from the firstdeflection bend substantially concentrically with and in the oppositedirection of the pipeline, preferably not in communication with thedeflection bend.
 2. The device in accordance with claim 1, wherein theblind pipe is connected to a lifting connection/pad eye at its oppositeend portion relative to the first bend.
 3. The device in accordance withclaim 1, wherein the first deflection bend is communicatingly connectedto a first remote connection, possibly via a first valve.
 4. The devicein accordance with claim 1, wherein the first deflection bend iscommunicatingly connected to a second remote connection, possibly via asecond valve.
 5. The device in accordance with claim 1, wherein at leastone of the remote connections is at a level slightly higher than thecenter line of the pipeline at the first bend.